﻿// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.

using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.ExternalAccess.FSharp.Classification
{
    internal interface IFSharpClassificationService
    {
        /// <summary>
        /// Produce the classifications for the span of text specified.  Classification should be
        /// performed as quickly as possible, and should process the text in a lexical fashion.
        /// This allows classification results to be shown to the user when a file is opened before
        /// any additional compiler information is available for the text.
        /// 
        /// Important: The classification should not consider the context the text exists in, and how
        /// that may affect the final classifications.  This may result in incorrect classification
        /// (i.e. identifiers being classified as keywords).  These incorrect results will be patched
        /// up when the lexical results are superseded by the calls to AddSyntacticClassifications.
        /// </summary>
        void AddLexicalClassifications(SourceText text, TextSpan textSpan, List<ClassifiedSpan> result, CancellationToken cancellationToken);

        /// <summary>
        /// Produce the classifications for the span of text specified.  The syntax of the document 
        /// can be accessed to provide more correct classifications.  For example, the syntax can
        /// be used to determine if a piece of text that looks like a keyword should actually be
        /// considered an identifier in its current context.
        /// </summary>
        Task AddSyntacticClassificationsAsync(Document document, TextSpan textSpan, List<ClassifiedSpan> result, CancellationToken cancellationToken);

        /// <summary>
        /// Produce the classifications for the span of text specified.  Semantics of the language
        /// can be used to provide richer information for constructs where syntax is insufficient.
        /// For example, semantic information can be used to determine if an identifier should be
        /// classified as a type, structure, or something else entirely. 
        /// </summary>
        Task AddSemanticClassificationsAsync(Document document, TextSpan textSpan, List<ClassifiedSpan> result, CancellationToken cancellationToken);

        /// <summary>
        /// Adjust a classification from a previous version of text accordingly based on the current
        /// text.  For example, if a piece of text was classified as an identifier in a previous version,
        /// but a character was added that would make it into a keyword, then indicate that here.
        /// 
        /// This allows the classified to quickly fix up old classifications as the user types.  These
        /// adjustments are allowed to be incorrect as they will be superseded by calls to get the
        /// syntactic and semantic classifications for this version later.
        /// </summary>
        ClassifiedSpan AdjustStaleClassification(SourceText text, ClassifiedSpan classifiedSpan);
    }
}
